How to get 3750 fps and a very lucky day

[Clark]

There's no problem getting 30 grains of H335 in a .223 case, how you might have done that I have no idea. 30 gr. of H335 behind a 53 gr. bullet would certainly produce the results that you got.
..

223 H335 55 gr left to right
unfired, extractor groove .329"
28 gr, extractor groove .329", 11% overload 69 kpsi
29 gr, extractor groove .329", 15% overload 80kpsi
30 gr, extractor groove .3295", 19% overload 92kpsi
31 gr, extractor groove .3320", 23% overload 106kpsi

30 gr would be right on the edge of short brass life.
The extractor groove may grow in one spot and grip the primer, so it does not fall out in another, but the brass is growing with every shot at that pressure.

 

[SteveNash]

It sounds to me like you have accidently dropped a live primer into one of your cases while you were loading...had the same thing happen with a shotgun.

Steve

 

[mcdoone]

I just bought two boxes of 6.5 x 47, was loading them right away. Happened to take a look inside the cases that I had already charged, and noticed one I hadn't got to yet appeared to have powder in it. On closer inspection, it wasn't powder. I found a small piece of newspaper wadded up inside, english print-couldn't ascertain the origin. Given the potential consequences, I will be checking all my new brass from all suppliers from now on.